our decades have passed since Pope John XXIII promised to throw open the windows of an ancient church.

Since Connie Miragliotta, then a young mother, dealt with her shock at seeing the familiar rituals of worship change by rejoicing in the promise that she would now be a greater part of church life.

Since Peggy Comfrey, then a brand-new nun, threw off the man's name and the head-to-toe habit she had taken on just four months earlier, and set out on a career in social justice.

Four decades have passed since 2,600 bishops, gathered in Rome for the Second Vatican Council, promised laypeople a new role in an old church.

And suddenly, Vatican II is again a current event. In the midst of the biggest crisis in the history of Catholicism in America, many laypeople are claiming the mantle of reform, demanding a role in reshaping a church that failed to stop the sexual abuse of thousands of young people over a period of decades.

And the hierarchy, backed by numerous laypeople and church intellectuals, is warning, in an echo of the debates of 40 years ago, that under that mantle of reform lurks an unacceptable spirit of revolution.

Social change has intensified in ways that John XXIII might not have anticipated, but so too has the church's resistance, fueled in part by a sense that its demographic heart is increasingly in the developing world, not the West. So as the forces clash again, the pressures that existed on both sides during Vatican II are more insistent.

"All these years, I haven't thought about Vatican II, until this crisis hit," said Peggie Thorp of Boston, a founder of the lay group Voice of the Faithful, who recalls the sight of men and women dancing at the altar celebrating the church council.

"But now, I think there's kind of a guilty feeling among all of us baby boomer laypeople," Thorp said. "We didn't take the ball and run with it when someone threw it to us. The substance of what was said at Vatican II was a wonderful invitation, and we're just trying to move it to the front of the agenda again."

That is exactly what some church leaders appear to fear.

The reaction is most vivid as bishops around the country clamp down on Voice of the Faithful, the group formed in Wellesley in response to the crisis. Although the group claims that it supports church teachings, top church officials are denouncing it in increasingly strident language. On Friday, the archbishop of Newark, John J. Myers, described Voice of the Faithful as "anti-church and, ultimately, anti-Catholic."

The Second Vatican Council, which ran four years from its start on Oct. 11, 1962, made dramatic changes in the ritual and theology of the Catholic Church. Symbolically, it is best remembered for the decisions to change the choreography of the Mass, directing priests to face the assembly and allowing Mass to be said in local languages, such as English, rather than universally in Latin.

Theologically, the council declared that the church includes all believers and not just the institution or the hierarchy, that the church's ministry requires social action, and that salvation is available to all, not just Catholics.

"It was a tremendous change," said historian and former seminarian Garry Wills, of Northwestern University. "Formerly, we still believed Jews were a cursed race, that democracy was an illegitimate form of government, and that there was no salvation outside the church. Vatican II wiped that away, and that kind of social change is going to have a deep and lasting effect -- the whole attitude toward authority has totally changed."

In the decades since Vatican II, the deference American Catholics show bishops has plummeted, according to several opinion polls. American Catholics openly began to dissent from a variety of church teachings, particularly on matters of sexual ethics, and many began to identify with their local churches and ignore their bishops.

But the sex abuse crisis made it impossible for many to continue to disregard church leadership.

"When the news started filtering in, I couldn't believe it, and I was hoping the hierarchy would turn to the laity to see if we could help," said Miragliotta, a 70-year-old retired divorce lawyer from North Andover. Miragliotta winters in Juno, Fla., and it was there that she realized earlier this year that every bishop in the short history of that diocese, Palm Beach, had been tainted by the sex abuse crisis. "No one wants to usurp their powers, but many of us have expertise, and I just want to be of service."

As lay activists mobilize to play a role in the future of their church, many have cited the symbols and words of Vatican II to assert their rights. Speaking not only at Voice of the Faithful meetings, but also at church gatherings, and at discussions of the crisis at Boston College and Regis College, they quote statements from Vatican II documents, such as "Christ ... fulfills his prophetic office ... not only by the hierarchy who teach in his name and with his authority, but also by the laity."

"These [bishops] were people we trusted, as if they were practically God, and they were allowing our children to be raped," said Anthony T. Massimini, who as a young priest from Philadelphia served as a page during the first session of Vatican II, and now, decades after he left the priesthood and married, is one of many thinkers advising Voice of the Faithful. "We still have no sense of talking to a bishop on an adult-to-adult basis. But something is going to change, because they're losing the people."

The bishops, however, are increasingly reasserting their authority as the church's official teachers, reminding their flock that the church is not a democracy. The most visible evidence is the increasing frequency with which bishops bar Voice of the Faithful from meeting in dioceses in New York, New Jersey, and Connecticut, and in parishes in Maine and Massachusetts.

Cardinal Bernard F. Law has not met with leaders of the group that has formed here, and has refused to take its money.

Law said yesterday that he is "in the process of learning more about the Voice of the Faithful" and is advising pastors not to allow new chapters to use church property. However, Law said he will let existing chapters meet in churches, and yesterday he reversed a ban on a chapter at St. Michael's Church in North Andover.

Once again, Voice of the Faithful members fall back on Vatican II as their best defense.

"The teachings of the Second Vatican Council clearly articulate the right of the laity to form associations and sets forth their obligation to make their voices heard on matters concerning the good of the church," Voice of the Faithful president James E. Post said in a letter to Emilio S. Allue, an auxiliary bishop in Boston.

But critics argue they are misreading the promise of Vatican II. Voice of the Faithful's most vocal opposition, a new group called Faithful Voice, also cites Catholic laws, such as one stating, "No initiative ... can lay claim to the title `Catholic' without the consent of the competent ecclesiastical authority."

"So much is justified in the name of Vatican II that is clearly contrary to the teachings and time-honored traditions of the Church," said Paul Koenen of Hingham. "I don't believe Vatican II had to end up as it did, but most of the people lobbying for change and the overhauling of the centuries-old, time-honored traditions seem to think Vatican II is on their side."

John XXIII died on June 3, 1963, after the first session of Vatican II. The current papacy, of John Paul II, is often described as "restorationist," a kind of reaction against the changes of Vatican II.

"The one area where Vatican II has had the hardest time moving forward is in the area of power -- Vatican II called for a decentralization of power, and that's the promise that has been withdrawn," said the Rev. Richard P. McBrien, a theologian at the University of Notre Dame.

But the Rev. Richard John Neuhaus, the editor of First Things, a monthly journal on religion and public life, disagreed.

"Vatican II had a lot to say about the role of the laity, but it was the role of the laity in evangelizing the culture," he said. "How many laypeople really can get excited that they, rather than Father Murphy, are going to decide that the church needs a new roof this year, rather than next year?"

Nevertheless, there have been remarkable changes in the role of laity in the church since Vatican II.

In an era of fewer and fewer priests, many parishes are administered by laypeople, and laypeople perform all but the sacramental tasks of church life. Parish councils -- some of which have real power; others of which are largely ignored -- abound, and laypeople serve on diocesan advisory boards on issues such as church finances. But theologians disagree about how much powersharing was promised by Vatican II.

Some Vatican II-era Catholics take the long view, arguing that the growing willingness of laypeople to speak up shows the success of the council, even as the crisis illustrates church failures. Four women who joined the Sisters of Saint Joseph of Boston around the time of Vatican II say the event dramatically changed their lives, but they are still looking for more.

"I see us in the midst of the dying of the pre-Vatican II life, and emerging into post-Vatican II life," said Sister Kathleen M. Hagerty.

And Sister Joanne Gallagher, who said the promise of Vatican II helped lead her to become a nun, said: "Forty years is nothing when you're trying to change the largest organization in the world -- systemic change is slow. The vision of Vatican II is a church where there's room for everybody, and that has kept me hopeful for the last 40 years."